RDL STGSP1 Data Sheet

STICK-ON® SERIES

Model ST-GSP1
Gated Speech Preamplifier

ANYWHERE YOU NEED...

• A Gated Mic-to-Line Preamplifier

• Speech Activated Gating

• Fast, Silent Audio Switching

• Integral Single-ended Noise Reduction

• Adjustable Gain and Threshold

• Balanced or Unbalanced Input / Output

• Phantom Power Provision

• Open-Collector Logic Output

You Need The ST-GSP1!

The ST-GSP1 is part of a group of products in the STICK-ON series from Radio Design Labs. The durable adhesives
provided with the ST-GSP1 permit permanent or removable mounting. Numerous available mounting accessories,
brackets and rack-mount chassis are optionally available to facilitate any system design. The ST-GSP1 offers the
ultimate in totally solid-state automatic mic switching, with a big plus, you can put it right where you need it!

APPLICATION: The ST-GSP1 is a gated-speech preamplifier designed to be used in a variety of situations where it
is desired to produce an automatically switched line-level signal from a microphone. This module may be used in
conjunction with other RDL modules to configure automatic mixing systems or may be used alone as a voice­operated module. The open-collector output may be used to trigger other equipment or RDL modules. The versatility
of ST-GSP1 applications range from complete automatic mixing system design to the addition of automatic mic gating
to the inputs of conventional mixers or amplifiers.

The mic input may be wired for balanced or unbalanced operation. A phantom voltage terminal is provided for use
with condenser microphones. The phantom inputs accept dc voltages up to 48 Vdc and are internally filtered. Most
microphones may run from the same 24 Vdc supply as the ST-GSP1. The audio output may also be wired balanced
or unbalanced. Two LED indicators are provided for adjustment. One LED indicates the correct gain setting. The
second indicator shows when the module is switched ON. Gain and threshold levels are adjusted using 25-turn
trimming potentiometer.

The mic input gain adjustment has sufficient range to accommodate a wide assortment of microphones, from low­output dynamic to higher-output condenser microphones. The threshold adjustment permits setting the audio level at
which the preamplifier output turns ON. Internal switching is solid-state and uses a soft-switch transition that sounds
instantaneous without annoying clicks or edge transitions. The module will mute 2 seconds after the audio level
drops below the preset threshold level. In circumstances where a longer delay time is desired, an external capacitor
may be connected to extend the delay.

A proprietary RDL circuit provides noise reduction whenever the mic is active. This circuit suppresses ambient noise
that permits higher audio levels before feedback and minimizes the audible open-mic effect during the 2 second off
delay.

Wherever a gated speech preamplifier is needed, the ST-GSP1 is the ideal choice. Use the ST-GSP1 in combination
with other RDL RACK-UP
system.

®

, STICK-ON®, TX™, or FLAT-PAK™ series products as part of a complete audio/video

RDL •• P.O. Box 1286 •• Carpinteria, CA., USA 93014 •• [phone] •• FAX [phone] •• http://www.rdlnet.com

STICK-ON® SERIES

Model ST-GSP1
Gated Speech Preamplifier

AUDIO WIRING

MIC INPUT PHNTM

SIGNAL

FROM

UNBALANCED

MIC-LEVEL

SOURCE

L
E

MIC INPUT

V
E
L

GATED SPEECH PREAMPLIFIER

PHNTM PWR

ALTERNATE

INPUTS

MIC INPUT PHNTM

SPEAKER

USED AS

MIC

LINE LEVEL OUTPUT

24V

S
L

DC

A

OUT

V
E

OUTPUT

G

D
E

A

L

T

A
Y

E

L
E

MIC INPUT

V
E
L

SIGNAL

FROM

BALANCED

MIC-LEVEL

SOURCE

POWER
WIRING

Installation/Operation

EN55103-1 E1-E5; EN55103-2 E1-E4

Typical Performance reflects product at publication time
exclusive of EMC data, if any, supplied with product.
Specifications are subject to change without notice.

GATED SPEECH PREAMPLIFIER

LINE LEVEL OUTPUT

PHNTM PWR

BALANCED
LINE-LEVEL
EQUIPMENT

SIGNAL

FEEDING

L
E
V
E
L

24V

DC

OUT

OUTPUT

S
L
A
V
E

OPTIONAL

CAPACITOR

GATED SPEECH PREAMPLIFIER

PHNTM PWR

LINE LEVEL OUTPUT

MIC INPUT

CAP DELAY

NONE 2 sec

4.7uF 3 sec

G

D
E

A

L
A
Y

10uF 4 sec

T
E

22uF 6.5 sec

47uF 11.5 sec
100uF 22 sec
220uF 60 sec

G

D

OUTPUT

E

24V

S
L

DC

A

OUT

V
E

A

L

T

A
Y

E

THIS
TERMINAL
IS COMMON
GROUND

ADJUST GATE FOR

DESIRED THRESHOLD

SENSITIVITY (CW

INCREASES

THRESHOLD AND

TRIGGERS ON

HIGHER LEVELS)

-+

BATTERY

OR EXTERNAL

PHANTOM

SUPPLY

(UP TO 48V)

ADJUST GAIN UNTIL

LED IS ON STEADY

DURING NORMAL

SPEECH

OR

OPTIONAL JUMPER
TO PROVIDE PHANTOM
VOLTAGE TO CONDENSER
MIC WHICH CAN USE UP
TO 32 VOLTS PHANTOM

1

ADJUSTMENT

THRESHOLD LEDGAIN LED

24 VDC

POWER

SOURCE

2

TYPICAL PERFORMANCE

Input Impedance: 150 to 600 Ω balanced, 5 kΩ unbalanced
Switching Time: 10 ms
Off delay: 2 sec. nominal (may be extended using external capacitor)
Control Signal: Open-Collector @ 50 mA
Headroom: > 18 dB (above +4 dBu)
THD+N: < 0.030% (1 kHz)
CMRR: > 45 dB
Freq. Response: 15 Hz to 20 kHz (+/- 0.5 dB into 10 kΩ bridging input)
Residual Noise: < -80 dB (below +4 dBu unweighted, preamp muted)
ON Gain: 45 to 65 dB (adjustable)
Power: 24 to 33 Vdc @ 75 mA, Ground referenced

Radio Design Labs Technical Support Centers

U.S.A. [phone], [phone]; Fax: [phone]

891-1006I

Europe [NH Amsterdam] (++31) 20-6238 983; Fax: (++31) 20-6225-287